A low-cost disposable label-free immunosensor for high-performance detection of indoxyl sulfate using chitosan based...

Indoxyl sulfate (IS) is a gut microbiota derived metabolite having various adverse implications in chronic kidney disease, cardiovascular disease, uremic syndrome. IS is also known as protein bound uremic toxin. Due to the serious issues caused by IS its timely quantification is important for the diagnosis and prevention of several diseases. Several traditional methods are available for detecting IS, including mass spectrometry and liquid chromatography. However, as these techniques are both time-consuming and costly our work represents the first demonstration of an electrochemical immunosensor for detecting IS using an anti-IS monoclonal antibody. The screen-printed carbon electrode (SPCE) was modified with a tertiary nanocomposite of chitosan-Au nanoparticles-CeO₂ nanoparticles to provide abundant chemical groups through chitosan for the immobilization of antibodies and to deliver the synergistic effects of the Au-CeO₂ nanocomposite such as improved surface area to volume ratio, electrical conductivity, and biocompatibility. The detection of IS using the fabricated label-free sensor was performed using the cyclic voltammetry technique. The fabricated sensor showed the sensitivity of 22.8 μA log₁₀ (μM) cm^-2 and LOD of 0.06 μM in the linear range of 1 nM to 1000 μM. The selectivity test was also performed on this immunosensor in the presence of various possible interference molecules found in human urine. The performance of the fabricated sensor was also assessed using a spiked urine sample, showing an acceptable recovery rate of 92.54-107.27%.